The aim of this work is to investigate the valorization of carbon dioxide through the CO₂ methanation and the CO₂ reforming of methane reactions. Alumina, ceria and mesoporous silica were chosen as the catalytic support materials. The wet impregnation technique was used in order to add an active phase of 15 xt% nickel (Ni), 1 wt% ruthenium (Ru) or a combination or the two metals (Ni-Ru) on each of the stabilized supports. The obtained catalysts were calcined at 550°C, and then characterized using X-Ray Diffraction (XRD), Nitrogen adsorption/desorption, H₂-Temperature Programmed Reduction (H₂-TPR), and CO₂-Temperature Programmed Desorption (CO₂-TPD). Characterization results of Ni and/or Ru catalysts supported on CeO₂, Al₂O₃, and KIT-6 showed that all supports and catalysts present a type IVa isotherms typical to mesoporous materials and that the formed RuO₂ species were well-dispersed when the CeO₂ is used as a support and in the bi-metallic catalysts. The reduction of NiO was enhanced in the presence of CeO₂ support given its redox properties. The presence of RuO₂ also led to a facilitated NiO reduction in the bi-metallic catalysts. In the CO₂ methanation reaction, a first part compared the catalytic activity of the different active phases on the same support. In each case, the bi-metallic Ni-Ru catalyst exhibited the highest conversions at 350°C which was linked to a possible good RuO₂ dispersion and NiO reducibility observed in these catalysts. Moreover, regardless of the active phase used, the catalytic activity of the catalysts depended on the type of the support. The order of reactivity obtained was : CeO₂ supported catalysts > KIT-6 suported catalysts > Al₂O₃ supported catalysts. In the second part, KIT-6 was promoted with different CeO₂ percentages and impregnated with the same studied active phases in an attempt to create more economical and stable catalysts. A good dispersion of RuO₂ species, an ameliorated active phase reducibility at lower temperatures, and an enhancement in the basic properties were observed following the promotion with Ce ans as the percentage of Ce in the catalyst increased. This ultimately led to higher catalytic performances especially for the bi-metallic 15Ni1Ru/CeₓKIT-6 catalysts. The stability study showed that the 15Ni1Ru/CeO₂ catalyst exhibited good catalytic activity in terms of CO₂ conversion (70%) and CH₄ selectivity (99%) and showed no deactivation for 24h on stream. In the CO₂ reforming of methane, CeO₂ supported catalysts showed lower catalytic activity when compared to Al₂O₃ supported catalysts. However, they showed more resistance to carbon formation as proven by the thermal analyses and the XRD performed on the spent catalysts. The effect of adding Ce to Al₂O₃ on the physico-chemical properties and the catalytic performances was then investigated. The addition of Ce was found to cause a partial destruction of the porous structure, strengthen the weak basic sites of the catalysts and enhance the catalytic activity. The 15Ni1Ru/Ce-Al₂O₃ catalyst showed higher activity and stability during a 12 hour stability test compared to the non-promoted counter-part. The three different mesoporous silicas (15Ni/KIT-6, 15Ni/SBA-15, 15Ni/SBA-16) were then synthesized using the wet impregnation technique, characterized and compared for their activity and stability in the CO₂ reforming reaction. In the dynamic tests, 15Ni/SBA-16 was the best performing catalyst due to its strong metal-support interactions and high contribution from strong basic sites. However, the 15Ni/KIT-6 catalyst was able to maintain a good activity and stability even at higher gas hourly space velocities GHSVs. Finally, among the Ni/Ce-KIT-6, 1Ru/Ce-KIT-6 and 15Ni1Ru/Ce-KIT-6 catalysts, the latter was the most active in the DRM reaction and maintained a stable high CO₂ conversion (97% for 12 hours). Despite the deposition of graphitic carbon during the stability test, the catalyst was not desactivated.